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Carburetor or timing?

MintysR4

Enthusiast
Messages
22
Location
Dublin
Hi all
Up to now the GTL has been running great then all of a sudden problems.
After a 10 mile drive home from work on a very cold morning I needed a touch of choke all the way to keep smooth.
When I got home I turned off the ignition and she ran on for a second and then a hissing noise.
She will start on full choke, revs seem higher than before, as soon as I try to ease off on the choke the revs increase and then it cuts out.
Any ideas, it has me stumped.
Thanks in advance and happy new year.
 
The revs going higher and not running unless the choke's out suggests a weakened mixture, confirmed by the "hissing" sound you heard that was air being sucked in by the engine through wherever the leak is. You need to find where the leak is, and one way is by using a WD40* aerosol can; once the engine's running spray the WD40* at the base of the carburettor & see if the engine tone or speed alters. If it does then your leak is around there somewhere. Do the same on the other pipes connecting to the carburettor and you ought to find the problem.

*="other aerosol based lubricants are available".
 
Hi Minty

The running on sounds like the ignition timing but the cause could be a number of things. I would start by checking the contact set, spark plugs, adjust/change and then check/adjust the timing. Once happy with the ignition side and if still not running well, I would investigate the carburettor side, check for sucking in of air: loose manifold nuts, manifold gasket damage, loose carb base nuts, carb base gaskets damaged, one way restrictor valve in hose back of base of carb not functioning or hose split.
 
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The revs going higher and not running unless the choke's out suggests a weakened mixture, confirmed by the "hissing" sound you heard that was air being sucked in by the engine through wherever the leak is. You need to find where the leak is, and one way is by using a WD40* aerosol can; once the engine's running spray the WD40* at the base of the carburettor & see if the engine tone or speed alters. If it does then your leak is around there somewhere. Do the same on the other pipes connecting to the carburettor and you ought to find the problem.

*="other aerosol based lubricants are available".
Thanks Andrew. That makes a lot of sense. I'll try that and let you know how I get on.
 
Hi Minty

The running on sounds like ignition timing but it could be a number of things. I would start by checking the contact set, spark plugs, adjust/change and then check/adjust the timing. Once happy with the ignition side and if still not running well, I would investigate the carburettor side, check for sucking in of air: loose manifold nuts, manifold gasket damage, loose carb base nuts, carb base gaskets damaged, one way restrictor valve in hose back of base of carb not functioning or hose split.
Thanks for that. It puzzled me that there was running on and then a hiss. I've been pointed in the direction of an air leak somewhere.
 
IMG_20210111_133113.jpgI think I found the problem, can I use a universal size tubing or is this a special part
 
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Hi Minty

That looks like the hose with the restrictor valve in it, which would tie in with the symptoms you outlined. If you feel along a bit from the hose clipped end of the hose, there should be a one way valve inside the hose. If the hose is only split at that end, you could cut it flush and you might have enough purchase to refit it with a new hose clip. If this is not feasible, I would source another hose.

Best Wishes
 
I trimmed it back as far as I could and fitted a new clip. It seems to be holding OK for the minute but it's fairly perished looking (a bit like myself). I'll go on the hunt for a new one.
Thanks again
 
I would advise fixing this first, THEN seeing if the car behaves better. If you adjust something else simultaneously you'll not know where you are and may become confused. Report back once the pipe's repaired first.
 
normal 8mm fuel hose works fine as long as you are careful pushing it onto the plastic T piece as they go brittle make sure you remove the Old plastic restriction please and fit it in the new rubber tubing otherwise you'll be back to square one with the same running issues
 
Thanks
I have a breather kit ordered from France. When it's fitted I'll try and adjust the carb
 
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